HT82K68 データシートの表示（PDF） - Holtek Semiconductor

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HT82K68

Multimedia Keyboard Encoder 8-Bit MCU

Holtek Semiconductor 

HT82K68E-L/HT82K68A-L

and reset by the SET [m].i and CLR [m].i instructions, re-

spectively. They are also indirectly accessible through

Memory pointer registers (MP0;01H, MP1;03H).

00H

In d ir e c t A d d r e s s in g R e g is te r 0

01H

M P0

02H

In d ir e c t A d d r e s s in g R e g is te r 1

03H

M P1

04H

05H

ACC

06H

PCL

07H

TB LP

08H

TB LH

09H

W D TS

0A H

STATU S

0B H

IN T C

0C H

0D H

TM R

0E H

TM R C

0FH

10H

11H

12H

PA

13H

PAC

14H

PB

15H

PBC

16H

PC

17H

PCC

18H

PD

19H

PDC

1A H

PE

1B H

PEC

1C H

S p e c ia l P u r p o s e

D a ta M e m o ry

20H

60H

G e n e ra l P u rp o s e

D a ta M e m o ry

(1 6 0 B y te s )

FFH

:U nused.

R e a d a s ²0 0 ²

RAM Mapping

Indirect Addressing Register

Location 00H and 02H are indirect addressing registers

that are not physically implemented. Any read/write op-

eration of [00H] and [02H] can access the data memory

pointed to by MP0 (01H) and MP1 (03H) respectively.

Reading location 00H or 02H indirectly will return the re-

sult 00H. Writing indirectly results in no operation.

The function of data movement between two indirect ad-

dressing registers is not supported. The memory pointer

registers, MP0 and MP1, are 8-bit registers which can

be used to access the data memory by combining corre-

sponding indirect addressing registers.

Accumulator

The accumulator is closely related to the ALU opera-

tions. It is also mapped to location 05H of the data mem-

ory and is capable of carrying out immediate data

operations. The data movement between two data

memory locations must pass through the accumulator.

Arithmetic and Logic Unit - ALU

This circuit performs 8-bit arithmetic and logic operation.

The ALU provides the following functions:

· Arithmetic operations (ADD, ADC, SUB, SBC, DAA)

· Logic operations (AND, OR, XOR, CPL)

· Rotation (RL, RR, RLC, RRC)

· Increment and Decrement (INC, DEC)

· Branch decision (SZ, SNZ, SIZ, SDZ ....)

The ALU not only saves the results of a data operation but

also changes the status register.

Status Register - Status

The 8-bit status register (0AH) contains the zero flag (Z),

carry flag (C), auxiliary carry flag (AC), overflow flag

(OV), power down flag (PDF) and watch dog time-out

flag (TO). The status register not only records the status

information but also controls the operation sequence.

With the exception of the TO and PDF flags, bits in the

status register can be altered by instructions like most

other registers. Any data written into the status register

will not change the TO or PDF flags. It should be noted

that operations related to the status register may give

different results from those intended. The TO and PDF

flags can only be changed by system power up, Watch-

dog Timer overflow, executing the HALT instruction and

clearing the Watchdog Timer.

The Z, OV, AC and C flags generally reflect the status of

the latest operations.

In addition, on entering an interrupt sequence or execut-

ing a subroutine call, the status register will not be auto-

matically pushed onto the stack. If the contents of status

are important and if the subroutine can corrupt the sta-

tus register, precaution must be taken to save it prop-

erly.

Rev. 1.40

8

February 1, 2011

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